fix(#812 follow-up): normalize detect-platform.sh host-match port comparison by scheme

gitea_url_matches_host compared every remote authority's port directly
against the configured HTTP(S) API URL's port, which conflated two
unrelated things and normalized default web ports asymmetrically:

- An SSH remote's transport port (e.g. ssh://git@host:2222/...) was
  compared against the configured HTTP(S) port, even though the SSH
  daemon port has nothing to do with the Gitea HTTP(S) API port.
- An explicit default port on the remote (https://host:443/...) failed
  to match an implicit (portless) configured URL, while the inverse
  (implicit remote vs. explicit configured) already matched -- the
  default-port equivalence was only applied on one side.

Fix get_remote_host() to strip an SSH transport port before it ever
reaches host-match, and make gitea_url_matches_host's default-port
normalization symmetric (":443" https / ":80" http is equivalent to
the implicit form on BOTH sides).

Adds red-first regressions for both repros to
test-pr-review-gitea-comment.sh (extending the #812 harness) and wires
that harness into packages/mosaic's test:framework-shell chain so it
runs under `pnpm test`.

Closes #850

packages/mosaic/framework/tools/git/detect-platform.sh

@@ -91,13 +91,19 @@ remote = urlparse(f"//{remote_host}")
 if configured.scheme not in {"http", "https"} or configured.hostname != remote.hostname:
     raise SystemExit(1)
 
-configured_port = configured.port
-remote_port = remote.port
-if remote_port is None:
-    default_port = 80 if configured.scheme == "http" else 443
-    if configured_port not in {None, default_port}:
-        raise SystemExit(1)
-elif configured_port != remote_port:
+# Normalize by scheme: an implicit (portless) HTTP(S) URL and its explicit
+# default-port form (":80" for http, ":443" for https) name the same
+# provider endpoint. Apply that equivalence symmetrically -- whichever side
+# omits the port is treated as carrying the scheme's default port -- so
+# "configured implicit vs. remote explicit" and "configured explicit vs.
+# remote implicit" both match. (The remote side here is always an HTTP(S)
+# authority; an SSH remote's transport port is stripped by get_remote_host
+# before reaching this comparison, since it identifies an unrelated
+# service on the same host, not the HTTP(S) provider port.)
+default_port = 80 if configured.scheme == "http" else 443
+normalized_configured = configured.port if configured.port is not None else default_port
+normalized_remote = remote.port if remote.port is not None else default_port
+if normalized_configured != normalized_remote:
     raise SystemExit(1)
 raise SystemExit(0)
 PY
@@ -432,7 +438,11 @@ get_remote_host() {
     fi
     if [[ "$remote_url" =~ ^ssh://([^/]+)/ ]]; then
         local host="${BASH_REMATCH[1]}"
-        echo "${host##*@}"
+        host="${host##*@}"
+        # Strip an SSH transport port (e.g. "git.example:2222"): it names the
+        # SSH daemon port, not the HTTP(S) provider API port, and must not
+        # feed gitea_url_matches_host's port comparison (#850).
+        echo "${host%%:*}"
         return 0
     fi
     if [[ "$remote_url" =~ ^git@([^:]+): ]]; then